Discovering that your favorite houseplant has become an ant colony’s new home is a common and frustrating problem. Ants trailing in and out of the drainage holes of a potted plant are a clear sign of an infestation.
The good news is that this is a solvable problem that doesn’t require harsh chemicals. Ants move into potted plants because the soil provides a perfect, insulated, and stable environment to establish a nest, safe from the elements and predators. The most effective way to get rid of them is to use a “soil drench” method that flushes the colony out without harming your plant.
The “Why”: Why Ants Choose Your Houseplant
Ants are not interested in eating your plant. They move into a potted plant for two primary reasons:
1. Ideal Nesting Site: The pot’s soil is loose, holds moisture, and is protected from the rain and heat of the outdoors. It’s a pre-made, perfect structure for a queen to establish a new colony or a satellite nest.
2. A Hidden Food Source: Many common houseplants are susceptible to sap-sucking insects like aphids, mealybugs, and scale. These pests secrete a sweet, sticky substance called “honeydew,” which is a primary food source for ants. The ants will actively “farm” these pests, protecting them from predators in exchange for the honeydew.
The Field-Tested Elimination Plan
This is a two-phase approach. First, you eliminate the ant colony, and second, you address the reason they were there in the first place.
#### Phase 1: The Insecticidal Soap Drench
This is the safest and most effective method for killing the ants in the soil without harming your plant’s roots.
1. Get the Right Product: You need a commercially formulated, pre-mixed insecticidal soap. These are available at any garden center. Do not use dish soap or other household detergents, as they can contain additives that can damage sensitive plant roots.
2. Prepare the Drench: In a bucket or large basin, mix the insecticidal soap with water according to the “soil drench” or “root drench” directions on the product label.
3. Take the Plant Outside: This process can be messy. Take the infested plant outdoors to a shaded area.
4. Drench the Soil: Slowly and thoroughly pour the insecticidal soap solution into the pot, allowing it to completely saturate the soil. Continue pouring until the solution flows freely from the drainage holes at the bottom of the pot. You will likely see ants begin to evacuate.
5. Let it Drain: Leave the plant in the shade for at least an hour to allow all the excess solution to drain away.
6. Rinse (Optional but Recommended): After an hour, you can gently flush the soil with plain water to rinse away any remaining soap residue.
#### Phase 2: Post-Treatment Inspection
* Check for Honeydew Pests: Once the ants are gone, carefully inspect your plant, especially the undersides of leaves and the joints where leaves meet the stem. Look for the tiny aphids, white cottony mealybugs, or bumpy scale insects that may have been the original attractant. If you find any, treat the plant’s foliage with the same insecticidal soap (as a spray this time) to eliminate the ants’ food source.
* Isolate the Plant: Keep the treated plant isolated from your other houseplants for a week or two to ensure no new ant activity appears.
FAQ
Q: Can I just submerge the whole pot in water to drown the ants?
A: This is a popular online suggestion, but it is not the best method. While it can work, submerging a plant’s root ball for an extended period (often 30+ minutes) can stress the plant by depriving the roots of oxygen, potentially leading to root rot. The insecticidal soap drench is faster and safer for the plant.
Q: Will putting coffee grounds or cinnamon on the soil get rid of them?
A: No. These are common myths. While a heavy layer of cinnamon or coffee grounds might act as a temporary deterrent and disrupt a foraging trail, it will not kill or eliminate an established ant colony that is living inside the pot’s soil.
Q: How can I prevent this from happening again?
A: The best prevention is to avoid leaving your houseplants outside on the ground for extended periods during the summer. This is the most common way ant colonies discover and move into them. When you do bring plants inside for the fall, carefully inspect the soil for any ant activity before you do. Regularly checking your plants for honeydew-producing pests will also make them less attractive to ants.